Competition Between SN2 and SN1 Reactions

It is possible to examine a particular reaction and determine whethei it is expected to proceed by an SN1 or an SN2 mechanism. 

The carbocation is stabilized (tertiary or resonance stabilized carbocations are best secondary carbocations are acceptable if other factors are favorable primary carbocations are not formed). 

Only poor nucleophiles are present (the absence of a good nucleophile slows the rate of a competing SN2 reaction). 

The electrophilic carbon is not sterically hindered (reactions at methyl and primary carbons are excellent reactions at secondary carbons are acceptable  

The solvent is aprotic (to make the nucleophile more reactive). 

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